Previous owned asset query

My wife and I gifted funds to our son to enable him to buy a flat. He will get rent from a spare bedroom which is covered by rent a room scheme. He wants to set up a joint bank account with me (father) into which the rent will be paid and into which he will pay a monthly amount. This account will be used to pay all the flat costs and anything left over will be contributed to his SIPP and ISA. He has asked me to administer the account so he doesn't get it mixed up with general living costs. I would like to confirm that this arrangement will not trigger a previously owned asset charge. I will gain nothing from the arrangement.

Hi,
Please contact the Inheritance Tax team for advice.
Inheritance Tax: general enquiries
Thank you.